Does skipping breakfast make you put on weight?

We’re often told that breakfast is an essential part of a healthy diet, especially if you are watching your weight. Some schools run breakfast to ensure that as many pupils as possible eat this all-important first meal of the day. But not everyone can stomach an early morning meal. In Europe and US between 10% and 30% of people skip breakfast, with teenage girls most likely to give it a miss, saying they’ve not got time, don’t feel hungry or that they’re on a diet.

Missing breakfast for dietary reasons runs counter to a great deal of advice. The logic goes that missing an early morning meal will leave you hungry for the rest of the day, tempting you to snack on high-calorie foods, and resulting in weight gain.

It’s a plausible theory, until you look for evidence that people who skip breakfast consume any more calories than anyone else. The impact skipping breakfast has on weight is harder to study systematically than you might expect. The first problem is how to define that first meal of the day. How much food counts as a real breakfast? Do you have to eat it seven days a week to be defined as a breakfast-eater? And how early in the day does it need to be eaten? For example, when the US Department of Agriculture conducted a systematic review on the topic they found that most studies defined breakfast as food eaten before ten in the morning. Anyone who ate at 10.05 was considered to have skipped breakfast, which could skew the results.

Another difficulty is that what is eaten for breakfast varies from country to country. In Scandinavia it might include smoked fish, in Germany cold meats, and in the UK boxed cereals, which can often contain more sugar and salt than people realise (the Consensus Action on Salt and Health group says some cereals are saltier than seawater). This makes the impact of eating breakfast more difficult to study on a global level because the nutritional benefits will depend on what you include in the meal.

But if we stick to looking at calories consumed, there have been many attempts to study the impact of eating breakfast on a person’s weight. A review of studies conducted before 2004 found that on the whole breakfast-skippers do not consume more calories during the rest of the day to compensate. People who ate breakfast tended to have a diet that was more nutritionally balanced, but it wasn’t more calorific. The findings on weight are a little more complex. Four studies found that children who didn’t eat breakfast had on average a higher body mass index, but another three studies found it made no difference. The advantage of those first four studies was that they had taken more trouble to control for factors which might skew the results. So the evidence begins to tip slightly towards a link between missing breakfast and increased weight.

To muddy the waters, a US review in 2011 cited five studies that found an association between breakfast-skipping and weight gain: three that found it made no difference, and one which found the opposite – that amongst overweight children, the breakfast-eaters weighed even more. And to confuse the issue even more, a meta-analysis which pooled the results of nineteen studies conducted in Asian and Pacific regions found a relationship between increased weight and missing breakfast. A European systematic review had similar findings, but one study found the relationship between breakfast-skipping and weight only existed for boys.

Does size matter?

What happens when you turn the question round? Seven studies found that overweight children are more likely to skip breakfast. But this highlights the problem with these studies – they are cross-sectional. They take a snapshot in time. They don’t prove causation. We can’t know which came first – the excess weight or the breakfast-skipping. Perhaps these children are missing breakfast because they are already overweight and are trying to eat less.